In one conventional and widely used leaf tobacco cutting procedure for the separation of tobacco lamina from stem material, the tobacco leaves are threshed and thereby the lamina are torn from the stem material. The tobacco lamina and stem then are separately stored for periods up to 2 years or longer. When desired to be used in cigarette making, the tobacco lamina are removed from storage and cut or shredded to the size desired in the cigarette making machine. The stored stem also may be used and, for this purpose, usually is flattened, cut and mixed in with the shredded tobacco to provide the cigarette making machine feed.
The threshing procedure which is effected in this prior art operation causes considerable damage to the tobacco, with large numbers of fines being formed. Large numbers of such fines are detrimental to the filling power of the tobacco and hence the net result of the threshing procedure is a decreased filling power of the tobacco in the cigarettes ultimately formed therefrom.
Another prior art procedure which has been used involves cutting the whole tobacco leaf transversely into long narrow strips or strands, disentangling the resultant mass and air separating the disentangled mass to separate heavier lamina strands containing stem particles from lighter lamina strands free from stem particles. Thereafter, threshing is effected on the heavier lamina strands to separate lamina and stem. The recovered lamina are passed to storage for subsequent feed to the cigarette making machine wherein the tobacco is shortened to the desired strand length prior to formation into cigarettes.
This procedure suffers from the drawbacks that the disentangling operation is not easily effected owing to the strand length of the tobacco and involves considerable tearing and hence degradation of the tobacco, that the air separation operation is inaccurate in achieving separation of stem from lamina owing to the large strand length of the particles being separated, and that strand shortening is required to be effected by the cigarette making machine.
A third prior art procedure, described in U.S. Pat. No. 3,128,775 involves subjecting the tobacco leaves to an initial transverse cut and then to a longitudinal cut to form a plurality of square or rectangularly-shaped tobacco pieces. These tobacco pieces are classified into a heavier fraction from having stem associated therewith and a light lamina fraction, the heavier fraction is subjected to threshing to separate the stem, and the light fraction lamina and the threshed lamina are stored. When required for use, the lamina is shredded to the desired shred size and passed to the cigarette making machine.
The latter procedure is an improvement on other prior art operations in that the individual tobacco pieces resulting from the cutting operation are much smaller and hence more readily separated and air classified. However, the latter procedure requires a separate shredding operation to be effected prior to passage of the tobacco to the cigarette making machine and the tobacco leaves must be smooth and flat for effective cutting to occur. Two separate cutting operations are used, necessitating complicated equipment.